Redundant QR code
Cobouw column by Marinus Aalberts
The Quick Response (QR) code is a two-dimensional barcode that was developed in Japan in the early 1990s. The advantage of the QR code is that, unlike the barcode, it is encoded in two directions, enabling redundancy to be built in. A damaged or incomplete QR code can still be read correctly because of this 'duplication' of information. In engineering, we often use redundancy to achieve a more reliable design; for example, a large building is designed so that it will not collapse if one column is suddenly removed. The power supply is made up of a national high-voltage interconnected network. And at home, we also have a backup in place, by entrusting a spare key to family or friends, just in case...
On Monday 31 January, Storm Corrie caused a high tide along the coast, resulting in the closure of three of the six storm surge barriers in the Netherlands. Of these six barriers, only the Hollandsche IJssel barrier has a double retaining structure (two lift gates, one behind the other). This makes the system more reliable: if the first lift gate fails to close, the second lift gate is there as a backup. The Haringvliet locks and the Eastern Scheldt barrier were also closed on Monday, but they only have a single retaining structure.
That doesn't mean, however, that there isn't redundancy at these locations, as there are several smaller retaining structures in place. If one of the locks fails to close, the water level behind the barrier need not be a major concern as not much water can ever pass through that one opening. But even if a storm surge barrier fails to close completely, i.e., if it stays open, it is not necessarily unsafe. The dykes behind the barrier can withstand water levels higher than those at which the barrier should have closed. That margin is smaller though, and there will be more flooding, but things won't go completely wrong straight away. Storm Corrie was not severe enough for that situation to occur.
Redundancy literally means ‘unnecessary’, which in turn means an additional layer of reliability. I will leave it to the politicians to decide whether the CTB's QR code is redundant. But it is certainly more reliable than a barcode.
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